A5021603154- Magnetic confinement fusion research
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Solar and Space Plasma Dynamics
- Laser-induced spectroscopy and plasma
- Plasma Diagnostics and Applications
- Atomic and Molecular Physics
- Nuclear reactor physics and engineering
- Fluid Dynamics and Turbulent Flows
- Oceanographic and Atmospheric Processes
- Mass Spectrometry Techniques and Applications
- High-pressure geophysics and materials
- Dust and Plasma Wave Phenomena
- Particle accelerators and beam dynamics
- X-ray Spectroscopy and Fluorescence Analysis
- Quantum chaos and dynamical systems
- Nonlinear Dynamics and Pattern Formation
- Metal and Thin Film Mechanics
- Electron and X-Ray Spectroscopy Techniques
- Target Tracking and Data Fusion in Sensor Networks
- Nuclear Engineering Thermal-Hydraulics
- Silicon and Solar Cell Technologies
- Geomagnetism and Paleomagnetism Studies
The University of Texas at Austin
2024
Fusion Academy
2017-2024
Fusion (United States)
2017-2024
New York University
2021-2023
Courant Institute of Mathematical Sciences
2021-2023
Massachusetts Institute of Technology
2016-2021
Plasma Technology (United States)
2017-2021
IIT@MIT
2017-2020
This paper presents investigations on the role of edge ion heat flux for transitions from L-mode to H-mode in Alcator C-Mod. Previous results ASDEX Upgrade tokamak indicated that a critical value per particle is needed transition. Analysis C-Mod data confirms this result. The indeed found increase linearly with density at given magnetic field and plasma current. Furthermore, indicate L-H transition also increases field. Combining yields general expression These are discussed point view...
A long-standing enigma in plasma transport has been resolved by modeling of cold-pulse experiments conducted on the Alcator C-Mod tokamak. Controlled edge cooling fusion plasmas triggers core electron heating time scales faster than an energy confinement time, which long interpreted as strong evidence nonlocal transport. This Letter shows that steady-state profiles, rise and disappearance at higher density measured these are successfully captured a recent local quasilinear turbulent model,...
We present a fully Bayesian approach for the inference of radial profiles impurity transport coefficients and compare its results to neoclassical, gyrofluid gyrokinetic modeling. Using nested sampling, (BITE) framework can handle complex parameter spaces with multiple possible solutions, offering great advantages in interpretative power reliability respect previously demonstrated methods. BITE employs forward model based on pySTRAHL package, built success well-known STRAHL code (Dux 2003...
Phenomenology of Ohmic energy confinement saturation in tokamaks is reviewed. Characteristics the linear (LOC) and saturated (SOC) regimes are documented transformations all transport channels across LOC/SOC transition described, including rotation reversals, 'non-local' cut-off density peaking, addition to dramatic changes fluctuation intensity. Unification results from nearly 20 devices indicates that occurs at a critical value product density, edge safety factor device major radius, this...
Abstract DIII-D physics research addresses critical challenges for the operation of ITER and next generation fusion energy devices. This is done through a focus on innovations to provide solutions high performance long pulse operation, coupled with fundamental plasma understanding model validation, drive scenario development by integrating core boundary plasmas. Substantial increases in off-axis current efficiency from an innovative top launch system EC power, pressure broadening Alfven...
New validation of global, nonlinear, ion-scale gyrokinetic simulations (GYRO) is carried out for L- and I-mode plasmas on Alcator C-Mod, utilizing heat fluxes, profile stiffness, temperature fluctuations. Previous work at C-Mod found that ITG/TEM-scale GYRO can match both electron ion fluxes within error bars in [White PoP 2015], suggesting multi-scale (cross-scale coupling) effects [Howard 2016] may be less important than L-mode. results presented here, however, show are able to the...
Perturbative transport experiments in magnetically confined plasmas have shown, for more than 20 years, that the injection of cold pulses at plasma edge can trigger increase core temperature. Predictive heat simulations with trapped gyro Landau fluid (TGLF) quasilinear model demonstrate temperature some regimes, and lack thereof other be explained by a change dominant linear micro-instability Alcator C-Mod. The effect density current on pulse are well captured TGLF, including relative...
Author(s): Cao, NM; Rice, JE; Diamond, PH; White, AE; Baek, SG; Chilenski, MA; Hughes, JW; Irby, J; Reinke, ML; Rodriguez-Fernandez, P; Team, Alcator C-Mod
This work introduces the “potential vorticity bucket brigade,” a mechanism for explaining resilience of vortex structures in magnetically confined fusion plasmas and geophysical flows. Drawing parallels with zonal jet formation, we show how inhomogeneous patterns mixing can reinforce, rather than destroy non-zonal flow structure. We accomplish this through an exact stochastic Lagrangian representation transport, together near-integrability property, which relates coherent topology to fluid...
Changes in the core intrinsic toroidal rotation velocity following L- to H- and I-mode transitions have been investigated Alcator C-Mod tokamak plasmas. The magnitude of co-current increments is found increase with pedestal temperature gradient , decrease magnetic field. These results are captured quantitatively by a model fluctuation entropy balance which gives Mach number an ITG turbulence dominant regime. agreement between experiment theory confidence for extrapolation future devices...
Abstract A dimensionless parameter dependence study of intrinsic torque has been performed on a database H- and I-mode plasmas from the Alcator C-Mod tokamak. The was determined by comparing angular momentum density profiles just before after L–H L–I transitions. found to scale as <?CDATA ${\beta }_{N}^{ 1.5}\enspace {\rho }_{{\ast}}^{-1.0}\enspace {\nu }_{{\ast}}^{0.1}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msubsup> <mml:mrow>...
The spontaneous emergence of structure is a ubiquitous process observed in fluid and plasma turbulence. These structures typically manifest as flows which remain coherent over range spatial temporal scales, resisting statistically homogeneous description. This work conducts computational theoretical study coherence turbulent the stochastically forced barotropic $\beta$ -plane quasi-geostrophic equations. equations serve prototypical two-dimensional model for Jovian atmospheres, can also be...
Transitionally turbulent flows frequently exhibit spatiotemporal intermittency, reflecting a complex interplay between driving forces, dissipation, and transport present in these systems. When this intermittency manifests as observable structures patterns the flow, characterization of turbulence systems becomes challenging due to nontrivial correlations introduced into statistics by structures. In work, we use tools from dynamical theory study Dimits shift regime flux-balanced...
Contemporary predictive models for heat and particle transport in tokamak plasmas are based on the assumption that local fluxes can be described terms of plasma parameters, where electromagnetic drift-wave-type turbulence is driven by gradients results cross-field transport. The question whether or not could dominated non-local certain circumstances essential our understanding magnetically confined plasmas, critical developing future tokamaks, such as ITER. Perturbative experiments using...
Analysis and modeling of rotation reversal hysteresis experiments show that a single turbulent bifurcation is responsible for the Linear to Saturated Ohmic Confinement (LOC/SOC) transition concomitant intrinsic on Alcator C-Mod. Plasmas either side exhibit different toroidal profiles therefore turbulence characteristics despite density temperature, which are indistinguishable within measurement uncertainty. Elements this also shown persist auxiliary heated L-modes. The deactivation...
X-ray spectra of n = 3–1 transitions in He-like ions (and satellites) from calcium, argon and chlorine have been measured the core Alcator C-Mod tokamak plasmas using high wavelength resolution x-ray spectrometer systems. The intensity ratio intercombination line y 3 (1s3p 3P1–1s2 1S0) to resonance w 1P1–1s2 is found be much larger than what expected if collisional excitation out ground state considered as only population mechanism for upper levels. This suggests that recombination cascades...
Abstract Emission lines which appear in the spectral ranges of ground state transitions from n = 2 levels He- and H-like argon ions are discussed. X-ray elements commonly found tokamaks (tungsten, molybdenum, iron sulphur) radiate wavelength range 3700–4000 mÅ identified by comparison with atomic structure calculations. Individual tungsten charge states vicinity Zn-like W 44+ documented, along B-like Mo 37+ . The behaviour line ratios as a function electron temperature is examined, support...
Optimized operation of fusion devices demands detailed understanding plasma transport, a problem that must be addressed with advances in both measurement and data analysis techniques. In this work, we adopt Bayesian inference methods to determine experimental particle leveraging opportunities from high-resolution He-like ion spectra tokamak plasma. The spectral fitting code is used analyze resonance (w), forbidden (z), intercombination (x, y), satellite (k, j) lines Ca following laser...
A profile for the critical gradient scale length (Lc) has been measured in L-mode discharges at Alcator C-Mod tokamak, where electrons were heated by an ion cyclotron range of frequency through minority heating with intention simultaneously varying heat flux and changing local gradient. The electron temperature (LTe−1 = |∇Te|/Te) was via BT-jog technique [Houshmandyar et al., Rev. Sci. Instrum. 87, 11E101 (2016)] it compared from power balance (TRANSP) analysis. Te profiles found to be very...
We present a Bayesian spectral fitting method developed for spectroscopic data analysis, particularly (but not solely) in the context of fusion energy research. The presented techniques are valuable to estimating moments and corresponding uncertainties whenever spectra result from line-integrated measurements nonuniform plasmas, which approximation atomic line shapes being ideal Gaussians gives poor estimates. decompose multiple, potentially overlapping lines into sum Gauss-Hermite...
X-ray spectra provide a wealth of information on high temperature plasmas; for example electron and density can be inferred from line intensity ratios. By using Johann spectrometer viewing the plasma, it is possible to construct profiles plasma parameters such as density, temperature, velocity with good spatial time resolution. However, benchmarking atomic code modeling obtained well-diagnosed laboratory plasmas important justify use determine when other independent diagnostics are not...
This work introduces the "potential vorticity bucket brigade," a mechanism for explaining resilience of vortex structures in magnetically confined fusion plasmas and geophysical flows. Drawing parallels with zonal jet formation, we show how inhomogeneous patterns mixing can reinforce, rather than destroy non-zonal flow structure. We accomplish this through an exact stochastic Lagrangian representation transport, together near-integrability property, which relates coherent topology to fluid...